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95-843 Service Oriented Architecture 1 Master of Information System Management 95-843 Service Oriented Architecture Web Services and REST.

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Presentation on theme: "95-843 Service Oriented Architecture 1 Master of Information System Management 95-843 Service Oriented Architecture Web Services and REST."— Presentation transcript:

1 95-843 Service Oriented Architecture 1 Master of Information System Management 95-843 Service Oriented Architecture Web Services and REST

2 95-843 Service Oriented Architecture Web Services One of the dominant paradigms for programming distributed systems. Enables business to business integration. (Suppose one organization uses CORBA and another uses.NET) No problem! Enables service oriented architecture (SOA). Adopted by the grid computing community. May exist internally to an organization or externally (in the cloud). 2 Master of Information System Management

3 95-843 Service Oriented Architecture What are Web Services? Web Services began life when Bill Gates introduced BizTalk in 1999. BizTalk was later renamed.NET. The idea: to provide the technologies to allow software in different places, written in different languages and resident on different platforms to connect and interoperate. From Programming the World Wide by Sebesta 3 Master of Information System Management

4 95-843 Service Oriented Architecture Two Approaches SOAP Based (WS-*) Web Services REST style web services Today we will look at the major principles of REST 4 Master of Information System Management

5 95-843 Service Oriented Architecture From WS-* to REST In this course we we have: (1) Created a SOAP based web service. (2) Tested it and retrieved its WSDL. (3) Generated code based on the WSDL. (4) Called that code from a client. Lets look at the REST design philosophy… 5 Master of Information System Management

6 95-843 Service Oriented Architecture REST REpresentational State Transfer Roy Fieldings doctoral dissertation (2000) Fielding (along with Tim Berners- Lee) designed HTTP and URIs. The question he tried to answer in his thesis was Why is the web so viral? What is its architecture? What are its principles? Master of Information System Management 6 Notes from RESTFul Java with JAX-RS by Bill Burke.

7 95-843 Service Oriented Architecture REST Architectural Principles The web has addressable resources. Each resource has a URI. The web has a uniform and constrained interface. HTTP, for example, has a small number of methods. Use these to manipulate resourses. The web is representation oriented – providing diverse formats. The web may be used to communicate statelessly – providing scalability Hypermedia is used as the engine of application state. Master of Information System Management 7

8 95-843 Service Oriented Architecture Understanding REST REST is not protocol specific. It is usually associated with HTTP but its principles are more general. SOAP and WS-* use HTTP strictly as a transport protocol. But HTTP may be used as a rich application protocol. Browsers usually use only a small part of HTTP. HTTP is a synchronous request/response network protocol used for distributed, collaborative, document based systems. Various message formats may be used – XML, JSON,.. Binary data may be included in the message body. Master of Information System Management 8

9 95-843 Service Oriented Architecture Principle: Addressability Addressability (not restricted to HTTP) Each HTTP request uses a URI. The format of a URI is well defined: scheme://host:port/path?queryString#fragment The scheme need not be HTTP. May be FTP or HTTPS. The host field may be a DNS name or a IP address. The port may be derived from the scheme. Using HTTP implies port 80. The path is a set of text segments delimited by the /. The queryString is a list of parameters represented as name=value pairs. Each pair is delimited by an &. The fragment is used to point to a particular place in a document. A space is represented with the + characters. Other characters use % followed by two hex digits. Master of Information System Management 9

10 95-843 Service Oriented Architecture Principle: Uniform Interface (1) A uniform constrained interface: - No action parameter in the URI - HTTP GET - read only operation - idempotent (once same as many) - safe (no important change to servers state) - may include parameters in the URI http://www.example.com/products?http://www.example.com/products pid=123 Master of Information System Management 10

11 95-843 Service Oriented Architecture Principle: Uniform Interface (2) HTTP PUT - store the message body - insert or update - idempotent - not safe Master of Information System Management 11

12 95-843 Service Oriented Architecture Principle: Uniform Interface (3) HTTP POST - Not idempotent - Not safe - Each method call may modify the resource in a unique way - The request may or may not contain additional information - The response may or may not contain additional information - The parameters are found within the request body (not within the URI) Master of Information System Management 12

13 95-843 Service Oriented Architecture Principle: Uniform Interface (4) HTTP DELETE - remove the resource - idempotent - Not safe - Each method call may modify the resource in a unique way - The request may or may not contain additional information - The response may or may not contain additional information HTTP HEAD, OPTIONS, TRACE and CONNECT are less important. Master of Information System Management 13

14 95-843 Service Oriented Architecture Principle: Uniform Interface (5) Does HTTP have too few operations? Note that SQL has only four operations: SELECT, INSERT, UPDATE and DELETE JMS and MOM have, essentially, two operations: SEND and RECEIVE SQL and JMS have been very useful. Master of Information System Management 14

15 95-843 Service Oriented Architecture What does a uniform interface buy? Familiarity We do not need a general IDL that describes a variety of method signatures. We already know the methods. Interoperability WS-* has been a moving target. HTTP is widely supported. Scalability Since GET is idempotent and safe, results may be cached by clients or proxy servers. Since PUT and DELETE are both idempotent neither the client or the server need worry about handling duplicate message delivery. Master of Information System Management 15

16 95-843 Service Oriented Architecture Principle: Representation Oriented(1) Representations of resources are exchanged. GET returns a representation. PUT and POST passes representations to the server so that underlying resources may change. Representations may be in many formats: XML, JSON, YAML, etc., … Master of Information System Management 16

17 95-843 Service Oriented Architecture Principle: Representation Oriented(2) HTTP uses the CONTENT-TYPE header to specify the message format the server is sending. The value of the CONTENT-TYPE is a MIME typed string. Versioning information may be included. Examples: text/plain text/html application/vnd+xml;version=1.1 vnd implies a vendor specific MIME type Master of Information System Management 17

18 95-843 Service Oriented Architecture Principle: Representation Oriented(3) The ACCEPT header in content negotiation. An AJAX request might include a request for JSON. A Java request might include a request for XML. Ruby might ask for YAML. Master of Information System Management 18

19 95-843 Service Oriented Architecture Principle: Communicate Statelessly The application may have state but there is no client session data stored on the server. If there is any session-specific data it should be held and maintained by the client and transferred to the server with each request as needed. The server is easier to scale. No replication of session data concerns. Master of Information System Management 19

20 95-843 Service Oriented Architecture Principle: HATEOAS Hypermedia as the Engine of Application State Hypermedia is document centric but with the additional feature of links. With each request returned from a server it tells you what interactions you can do next as well as where you can go to transition the state of your application. Example: http://…/customers/3214 5 http://…/products/111 Master of Information System Management 20

21 95-843 Service Oriented Architecture Principle: HATEOS From Wikipedia: A REST client enters a REST application through a simple fixedURL. All future actions the client may take are discovered within resource representations returned from the server. The media types used for these representations, and the link relations they may contain, are standardized. The client transitions through application states by selecting from the links within a representation or by manipulating the representation in other ways afforded by its media type. In this way, RESTful interaction is driven by hypermedia, rather than out-of-band information.[1] 21 Master of Information System Management

22 95-843 Service Oriented Architecture Principle: HATEOS Knock Knock Joke Example Netbeans RESTKnocker 22 Master of Information System Management

23 95-843 Service Oriented Architecture Bing Maps Using REST Visit the URL (using my key): http://dev.virtualearth.net/REST/v1/Locations/New%20York?output=xml&key=AqMWEeRufD1Ch 2uhYsyD10OPbLGMs_GATcB8Xd8trcvybpNuDRcMo6U6uVCqOara How does your browser react? Why? Change XML to JSON. How does your browser react? Why? 23 Master of Information System Management

24 95-843 Service Oriented Architecture WeatherBug API Here is a nice description of the weather bug REST style API: http://developer.weatherbug.com/docs/read/WeatherB ug_API_JSONhttp://developer.weatherbug.com/docs/read/WeatherB ug_API_JSON WeatherBug also provides a SOAP based service. 24 Master of Information System Management


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